JP2000335887A - Crane jib derricking and telescope device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a cylinder speed at the same level both in derricking action and in telescoping action for letting falling and telescopic action of a jib coincide with rising and contracting action in a falling direction of an operation lever. SOLUTION: This device is provided with a derricking cylinder to let a jib derrick from the underside, an expansion cylinder 19 to telescoping the jig, a change-over switch 23, a derricking switching valve gear 25 switched by the change-over switch 23, and a hydraulic pressure direction switching valve 29 to supply hydraulic oil to either of both cylinders through the switching valve gear 25 to be capable of switching between a first and a second switching positions in accordance with a tilting direction of the operation lever. The first switching position hydraulic oil side is connected to the bottom side of both cylinders, and the second switching position hydraulic oil side is connected to the head side of both cylinders. A reversing means 30 interlocked with operation of the change-over switch 23 to reverse a switching action direction of the hydraulic pressure direction switching valve 29 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jib hoisting and retracting device for a crane. More specifically, the present invention relates to a crane jib hoisting / contracting device for raising / lowering and moving a telescopic jib attached to a tip of a telescopic boom so as to be able to raise / lower.

[0002]

2. Description of the Related Art A self-propelled crane in which a telescopic boom is pivotally supported on a swivel table mounted on a vehicle so as to be able to raise and lower, and a telescopic jib is attached to the tip of the telescopic boom so as to be able to raise and lower, A jib drive control device described in Japanese Utility Model Registration No. 2566667 is known as a jib raising / lowering / extending / contracting device for expanding / contracting movement. As shown in FIG. 7, this jib drive control device includes an up-and-down cylinder 1 for raising and lowering a jib (not shown), a telescopic cylinder 2 for expanding and contracting the jib (a fixed end on the piston rod side), and A four-way three-position switching valve 4 provided in an operator's cab (not shown) and operated by a tilting operation of an operation lever 3 and an operation switch (not shown) provided in the operator's cab and remotely operated. Is connected to a pair of control ports of the four-way three-position switching valve 4 via two hydraulic hoses 5A and 5B which can be extended and retracted in conjunction with the extension and retraction of the telescopic boom. Cylinder 2
Each of the oil chambers is provided with a valve device 8 connected via oil passages 6A, 6B, 7A, 7B.

Here, the up-and-down cylinder 1 is supported between the end of the telescopic boom and the jib so as to suspend the jib from above. The telescopic cylinder 2 is housed in a jib. The valve device 8 includes two switching valves 8
A, 8B, and when these switching valves 8A, 8B are switched to one switching position, as shown by a solid line in the figure, one of the two hydraulic hoses 5A, 5B is oiled. The other hose 5B is connected to an oil chamber on the jib raising operation side of the up-and-down cylinder 1 via an oil path 7A via a passage 6A, and the switching valve 8A , 8B are switched to the other switching position, the one hose 5A is connected to the compression operation side oil chamber of the telescopic cylinder 2 via the oil passage 6B, as shown by the dotted line in the figure. The hose 5B is configured to be connected to an extension operation side oil chamber of the telescopic cylinder 2 via an oil passage 7B.

[0004] Therefore, by operating the four-way three-position switching valve 4 by the operating lever 3, the undulating cylinder 1 is switched.
And the drive direction of the telescopic cylinder 2 can be selected, and the valve device 8 remotely controlled by an operation switch selects whether the cylinder to be driven is the undulating cylinder 1 or the telescopic cylinder 2. be able to. Therefore, by operating the operation switch by tilting the operation lever 3 forward, it is possible to perform the downward movement and extension operation of the jib, and to operate the operation switch by tilting the operation lever 3 backward. Thus, the jib raising and contracting operations can be performed. That is, the operation direction of the operation lever 3 can be made to coincide with the operation direction of the operation lever at the time of the up-and-down movement of the telescopic boom and the telescopic operation.

[0005]

In the above-mentioned conventional jib drive control device, since the switching direction of the four-way three-position switching valve 4 is determined with respect to the tilting direction of the operation lever 3, the operation lever 3 is tilted forward. When the jib is operated to extend and retract when operated, and when the operation lever 3 is operated to tilt backward and backward, the four-way three-position switching valve 4 also switches between extension and contraction.
Therefore, unlike the conventional crane structure, between the tip of the telescopic boom and the jib, when the up-and-down cylinder 1 attempts to apply the conventional jib drive control device to the up-and-down type that raises and lowers the jib from below, When the operating lever 3 is tilted forward, the jib is raised, and when the operating lever 3 is tilted backward, the jib is lowered. Therefore, the operating direction of the operating lever is different from the operating direction of the operating lever when the telescopic boom is raised and lowered. Problem.

In order to solve this problem, the piping may be changed in accordance with the operation direction of the operation lever 3. That is, as shown in FIG. 8, the pressure oil side at one switching position 4a of the four-way three-position switching valve 4 is connected to the bottom side of the up-and-down cylinder 1 (upward operation side) and the head side of the telescopic cylinder 2 (compression operation side).
And the pressure oil side of the other switching position 4b may be connected to the head side (lower operation side) of the up-and-down cylinder 1 and the bottom side (extension operation side) of the telescopic cylinder 2. However, this leaves a problem that the cylinder speed cannot be adjusted.

That is, in FIG. 8, first, the undulating speed of the undulating cylinder 1 is considered. Assuming that the area ratio (Ah: Ab) of the head side area Ah and the bottom side area Ab of the undulating cylinder 1 is 1: 3, the pressure oil discharge amount Q1 at the one switching position 4a of the four-way three-position switching valve 4 and the other one. If the pressure oil discharge amount Q2 at the switching position 4b is Q1 ≒ 3 · Q2, the speed at the time of the starting operation and the speed at the time of the descending operation become the same. However, consider the expansion / contraction speed of the telescopic cylinder 2 here. Similarly, if the area ratio (Ah: Ab) between the head side area Ah and the bottom side area Ab is 1: 3, the speed during the contraction operation is Q1 / Ah, and the speed during the expansion operation is Q2 / Ab. Here, Q1 ≒ 3 · Q
2. When Ah = Ab / 3 is substituted, the speed at the time of the contraction operation is 9
Q2 / Ab, which is 9 times the speed during the stretching operation. Further, since Q2 is smaller than Q1 ≒ 3 · Q2, the speed at the time of the extension operation becomes very slow.

It is an object of the present invention to provide a crane jib hoisting / contracting device which can solve these problems.

[0009]

Means for Solving the Problems A jib hoisting and expanding / contracting device for a crane according to the present invention employs the following configuration to achieve the above object. The invention according to claim 1 is a crane jib hoisting / elongating / contracting device that raises / lowers telescopically movable extensible jib supported at the tip of a boom via a support shaft. A lifting cylinder for raising and lowering the jib, a telescopic cylinder for expanding and contracting the jib, a changeover switch, a raising and lowering changeover switching valve device switched by the changeover switch, and an operation lever capable of tilting and returning to a neutral position And a hydraulic pressure direction that switches between a first switching position and a second switching position in accordance with the tilt direction of the operating lever, while supplying pressure oil to either the lifting cylinder or the telescopic cylinder through the lifting / contracting switching valve device. A switching valve, wherein the pressure side of the first switching position of the hydraulic direction switching valve is connected to the up-down cylinder and the extension cylinder via the up-down / expansion switching valve device. A second switching position pressure oil side of the hydraulic direction switching valve is connected to a bottom side of the cylinder, and is connected to a head side of the up / down cylinder and the telescopic cylinder via the up / down / expansion / retraction switching valve device. It has a reversing means for reversing the switching operation direction of the hydraulic direction switching valve in conjunction therewith.

According to the present invention, the first of the hydraulic directional switching valves is provided.
The pressure oil side of the switching position is connected to the bottom side of the raising / lowering cylinder and the telescopic cylinder via an up / down switching valve device, respectively, and the hydraulic pressure side of the second switching position of the hydraulic directional switching valve is via an up / down switching valve device. Since the cylinder is connected to the head side of the up-and-down cylinder and the telescopic cylinder, respectively, the speed of the cylinder can be set to the same level both during the up-down operation and during the telescopic operation. In addition, since the reversing means for reversing the switching operation direction of the hydraulic direction switching valve in conjunction with the operation of the changeover switch is provided, it is necessary to make the extension / retraction operation of the jib coincide with the tilting direction of the operation lever. Can be. For example, when the operation lever is tilted forward, the jib can be turned up and down, and when the operation lever is tilted backward, the jib can be moved up and down. Therefore, the operation direction of the operation lever at the time of raising and lowering the telescopic boom and at the time of the telescopic operation can be made to coincide with each other.

According to a second aspect of the present invention, in the crane jib hoisting and retracting device according to the first aspect, the hydraulic direction switching valve is formed by a four-port three-position switching valve controlled to be switched by pilot pressure. , The inversion means,
A pilot pressure is supplied to the four-port three-position switching valve based on the tilting operation of the operation lever, and is inserted in the middle of a pilot pressure oil passage for switching the four-port three-position switching valve. Is formed by a four-port two-position switching valve that is switched in conjunction with. According to the present invention, the four-port two-position switching valve that is switched in conjunction with the switching operation of the selector switch supplies the pilot pressure to the four-port three-position switching valve based on the tilting operation of the operation lever, and the fourth port switches. Since it is inserted in the middle of the pilot pressure oil passage for switching the port 3 position switching valve, for example, the forward tilt operation (bend / extend operation) / backward tilt operation (elevation / retraction operation) of the operation lever is performed at the 4 port 3 position. Since the switching valve is changed to the cylinder retracting operation position / extension operation position, the up / down and extension / retraction operation of the jib can be matched with the tilting direction of the operation lever. Therefore, with a relatively simple configuration, the risk of erroneous operation can be reduced.

According to a third aspect of the present invention, in the crane jib hoisting / contracting device according to the first aspect, the hydraulic direction switching valve is formed by a four-port three-position switching valve controlled to be switched by pilot pressure. The operating lever is formed by an electric operating lever that outputs a current having a magnitude corresponding to a tilting direction and a tilting angle, and the reversing means includes a pair of control levers for controlling a pilot pressure supplied to the four-port three-position switching valve. And a pair of electromagnetic pilot pressure control valves connected to the pair of electromagnetic pilot pressure control valves and both output terminals of the operation lever and switched in conjunction with the operation of the changeover switch. It is characterized by being formed from a pair of switching relays for switching the connection between the valve and the output terminals of the operation lever.
According to this invention, the effect described in claim 2 can also be achieved by the configuration of the electric operation lever, the pair of electromagnetic pilot pressure control valves, and the pair of switching relays.

According to a fourth aspect of the present invention, there is provided a jib hoisting / contracting device for a crane for raising and lowering an extensible jib supported on a tip end of a boom via a support shaft so as to be capable of raising and lowering. An up-and-down cylinder for raising and lowering the jib below the shaft, a telescopic cylinder for extending and retracting the jib, a changeover switch, an up-and-down / expansion changeover switching valve device switched by the changeover switch, and a tiltable and returnable to a neutral position. And pressurized oil to one of the up-and-down cylinder and the telescopic cylinder through the up-and-down / expansion switching valve device, and switch to the first switching position and the second switching position in accordance with the tilt direction of the operating lever. And a first switching position pressure oil side of the hydraulic direction switching valve through the up / down switching valve device. And the second switching position pressure oil side of the hydraulic direction switching valve is connected to the head side of the up / down cylinder and the telescopic cylinder via the up / down switching valve device, A switching valve provided between the switching valve and the up / down / expansion switching valve device, the switching valve switching a flow direction of the hydraulic oil from the hydraulic direction switching valve in conjunction with an operation of the switching switch. I do.

According to the present invention, the flow direction of the pressure oil from the hydraulic direction switching valve can be switched by the switching valve provided between the hydraulic direction switching valve and the up / down / expansion switching valve device. According to the configuration, the extension and retraction of the jib can be matched with the tilting direction of the operation lever.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing an entire crane according to an embodiment of the present invention, and FIG. 2 is a view showing a state where a telescopic boom and a jib of the crane are extended. In these figures, a swivel 12 is provided on a vehicle 11 so as to be able to swivel, and an extensible telescopic boom 13 is supported on the swivel 12 so as to be able to undulate. A bracket 15 is pivotally mounted on a tip of the telescopic boom 13 with a pivot 14 as a fulcrum. A jib 17 is supported on the tip of the bracket 15 via a support shaft 16 so as to be able to undulate.

FIG. 3 shows the bracket 15 and the jib 17.
It is an enlarged view of a part. In FIG.
An up / down cylinder 18 is connected between the jib 5 and the jib 17 and below the support shaft 16. Thus, the jib 17 is raised and lowered with the support shaft 16 as a fulcrum.
The jib 17 is formed to be extendable and contractable from an outer cylinder 17A and an inner cylinder 17B housed in the outer cylinder 17A. A telescopic cylinder 1 is provided between the outer cylinder 17A and the inner cylinder 17B.
9 is built-in. Thereby, the jib 7 is extended and contracted.

FIG. 4 shows a jib hoisting / contracting device for raising / lowering the jib. Jib hoisting and stretching device 20
Is a hoisting cylinder device 21 including the hoisting cylinder 18
And a telescopic cylinder device 22 including the telescopic cylinder 19
A changeover switch 23, an up / down / expansion changeover valve device 25 connected to the changeover switch 23 via a cord 24 (wound around a cord reel 24 </ b> A) and switched by the changeover switch 23, a tiltable and neutral switch The operation lever 26 which can be returned to the position, is connected to the undulation / expansion switching valve device 25 via two hydraulic hoses 27, 28 (wound by hose reels 27A, 28A), and the undulation / extension switching is performed. A hydraulic directional switching valve 29 for supplying pressure oil to one of the up-and-down cylinder 18 and the telescopic cylinder 19 through a valve device 25, and a switching operation direction of the hydraulic directional switching valve 29 in conjunction with the operation of the switch 23. And a reversing means 30 for performing the inversion.

The up / down cylinder device 21 includes the up / down cylinder 18 and a pair of counter balance valves 31 and 32 connected to the head side and the bottom side of the up / down cylinder 18, respectively. The telescopic cylinder device 22 includes the telescopic cylinder 19 and a pair of counter balance valves 33 and 34 connected to the head side and the bottom side of the telescopic cylinder 19, respectively. The changeover switch 23 is connected to the swivel 2
It is provided in a driver's cab (not shown) provided above, and is configured to be switchable between an up-and-down position and an extendable position where the jib 17 is moved up and down and extended and retracted.

The up / down / expansion switching valve device 25 includes a first four-port two-position switching valve 41 and a second four-port two-position switching valve 42. First 4 ports 2
The position switching valve 41 has a solenoid 41a that is energized through the cord 24 when the switch 23 is switched to the telescopic position, and is located at the first switching position 41b when the solenoid 41a is not energized. 2
7 is connected to the bottom side of the undulating cylinder 18, and the hydraulic hose 28 is connected to the head side of the undulating cylinder 18, respectively.
When the solenoid 41a is energized, it is switched to the second switching position (stop position) 41c. The second 4-port 2-position switching valve 42 has a solenoid 42a that is energized through the cord 24 when the switch 23 is switched to the telescopic position. When the solenoid 42a is not energized, the first switching position ( (Stop position) 42b, but the second switching position 42c when the solenoid 42a is energized.
The hydraulic hose 27 is connected to the bottom side of the telescopic cylinder 19, and the hydraulic hose 28 is connected to the head side of the telescopic cylinder 19, respectively.

The hydraulic direction switching valve 29 is provided at the stop position 5.
1a according to the tilt direction of the operation lever 26,
4-port pilot pressure switching control that switches between a switching position (cylinder extension / extension operation position) 51b and a second switching position (cylinder retracting operation position) 51c, and that proportionally controls the flow rate according to the tilt angle of the operation lever 26. It is formed by a three-position switching valve 51. Specifically, when the four-port three-position switching valve 51 is switched to the first switching position (cylinder extension operation position) 51b, the pump oil passage 52 is connected to the hydraulic hose 27, and the tank oil passage 53 is connected to the hydraulic hose 28. Connected. In other words, the first switching position (cylinder extension / extension operation position) side pressure oil is connected to the bottom sides of the up / down cylinder 18 and the extendable cylinder 19 via the up / down / expansion switching valve device 25, respectively. On the other hand, when switched to the second switching position (cylinder retracting operation position) 51c, the pump oil passage 52 is connected to the hydraulic hose 28, and the tank oil passage 53 is connected to the hydraulic hose 27, respectively. That is, the pressure oil at the second switching position (cylinder retracting operation position) is connected to the head side of the retractable cylinder 18 and the retractable cylinder 19 via the retractable / expandable switching valve device 25, respectively.

The reversing means 30 is connected to the operation lever 26.
Pilot pressure oil passages 61A and 61 for supplying pilot pressure to the 4-port 3-position switching valve 51 based on the tilting operation of
B, 62 </ b> A, 62 </ b> B, which is inserted in the middle and is switched based on the switching operation of the switch 23.
The position switching valve 63 is formed. The four-port two-position switching valve 63 has a solenoid 63a that is energized through the cord 24 when the switch 23 is switched to the telescopic position, and is located at the first switching position 63b when the solenoid 63a is not energized. , An oil passage 61A through an oil passage 61B,
d, the oil passage 62A is connected to the pilot pressure introduction portion 51e of the switching valve 51 via the oil passage 62B, while the solenoid 63a is switched to the second switching position 63c when energized, and the oil passage 61A is connected to the pilot pressure through the oil passage 62B. The oil passage 62A is connected to the pilot pressure introduction portion 51d through the oil passage 61B to the introduction portion 51e.

When the operating lever 26 is tilted backward (expanded or contracted), the oil passage 61A is connected to the pump oil passage 6 through the valve 64.
6 is connected. Thus, when the operation lever 26 is tilted backward, the four-port three-position switching valve 51 is switched to the first switching position (cylinder extension / extension operation position) 51b while the switch 23 is in the up / down position. When the changeover switch 23 is switched to the telescopic position, the four-port three-position switching valve 51 is switched to the second switching position (cylinder retracting operation position) 51c. That is, the switching operation direction of the 4-port 3-position switching valve 51 is reversed. The oil passage 6
2A is connected to the pump oil passage 66 through the valve 65 when the operation lever 26 is tilted forward (downward and forward). Thus, when the operation lever 26 is tilted forward, the four-port three-position switching valve 51 is switched to the second switching position (cylinder retracting operation position) 51c in a state where the switch 23 is switched to the up / down position. On the other hand, when the changeover switch 23 is switched to the telescopic position, the four-port three-position changeover valve 51 is set to the first changeover position (cylinder retracting operation position) 51.
b. That is, the 4 port 3 position switching valve 5
1, the switching operation direction is reversed. These oil passages 6
Pressure switches 67 and 68 for detecting the tilt direction of the operation lever 26 are provided in the middle of 1A and 62A, respectively. It should be noted that the pressure switch 67 can detect by switching between rising and contracting, and the pressure switch 68 can detect by switching between lowering and extending by a signal from the changeover switch 23.

In such a configuration, the amount of pressure oil discharged from the second switching position (cylinder retracting operation position) of the four-port three-position switching valve 51 is Q1, and the amount of pressure oil discharged from the first switching position (cylinder extending / extending operation position) is Q1. Is Q2, the bottom side area of the up / down cylinder 18 is Ab, and the head side area is Ah, the speed at the time of the lowering operation is Q1 / Ah, and the speed at the time of the raising operation is Q2 / Ab. Here, if the speed at the time of the down motion is the same as the speed at the time of the up motion, the usability is good, so Q1 = (Ah / Ab)
Q1 and Q2 are set so as to be Q2. This includes
The flow rate may be set by providing a throttle valve or the like in the middle of each of the hydraulic hoses 27 and 28, or the flow rate may be set by changing the internal flow path cross section of the 4-port 3-position switching valve 51.

In the state where the flow rates Q1 and Q2 are set as described above, the expansion and contraction speed of the expansion and contraction cylinder 19 is Q1 / Sh and the expansion and contraction speed is Q1 / Sh.
2 / Sb. Here, Sh and Sb are the head-side area and the bottom-side area of the telescopic cylinder 19. Where Q
When 1 = (Ah / Ab) / Q2 is substituted, the speed at the time of the contraction operation is (Ah / Ab) × (Q2 / Sh), and the speed of the expansion / contraction is (Ah / Ab) × (Q2 / Sh) = Q2 / Sb,
That is, it becomes the same when (Ah / Ab) = (Sh / Sb). Here, since (Ah / Ab) ≒ (Sh / Sb) is usually set to 3 to 4, the difference in the speed of the undulation is the same level in the expansion and contraction.

According to this embodiment, the pressure oil on the first switching position (cylinder extension / extension operation position) side of the 4-port 3-position switching valve 51 is supplied to the up / down cylinder 18 via the up / down switching valve device 25.
The pressure oil is connected to the bottom side of the telescopic cylinder 19 and the second switching position (cylinder retracting operation position) of the four-port three-position switching valve 51. Telescopic cylinder 1
9 are connected to the head side respectively, so that the speed of the cylinder can be set to the same level at the time of the undulating operation and the expanding and contracting operation.

Further, since the reversing means 30 for reversing the switching operation direction of the four-port three-position switching valve 51 in conjunction with the operation of the changeover switch 23 is provided, the jib 17 is tilted in the tilting direction of the operation lever 26. The extension operation and the expansion / contraction operation can be matched. That is, when the operation lever 26 is tilted forward, the jib 17 can be turned up and down.
When the operation lever 26 is tilted rearward, the jib 17 can be made to perform a retracting operation. Therefore, the operation direction of the operation lever at the time of raising and lowering of the telescopic boom and at the time of telescopic operation can be made to coincide with each other, so that the risk of erroneous operation can be reduced.

A four-port two-position switching valve 63 that is switched in conjunction with the switching operation of the selector switch 23 supplies a pilot pressure to the four-port three-position switching valve 51 based on the tilting operation of the operation lever 26. 4 port 3 position switching valve 5
1 for switching operation of the pilot pressure oil passages 61A and 61B,
Since it is inserted in the middle of 62A, 62B, for example, the forward tilting operation (lowering / extending operation) / backward tilting operation (elevation / retraction operation) of the operation lever 26 is performed in the 4-port 3-position switching valve 51 by the cylinder retracting operation position. Since the position is changed to the / extension operation position, the up / down and extension / retraction operations of the jib 17 can be made to coincide with the tilt direction of the operation lever 26. Therefore, erroneous operations can be reduced with a relatively simple configuration.

In the above-described embodiment, the reversing means 30 is constituted by the four-port two-position switching valve 63. However, the invention is not limited to this. For example, a structure as shown in FIG. 5 or FIG. In the structure shown in FIG. 5, first, the operation lever is formed by an electric operation lever 26A that outputs a current having a magnitude corresponding to the tilt direction and the tilt angle. The reversing means 30 includes a pair of electromagnetic pilot pressure control valves 71 and 72 for controlling the pilot pressure supplied to the four-port three-position switching valve 51, a pair of the electromagnetic pilot pressure control valves 71 and 72, and an operating lever. 26A, and a pair of electromagnetic pilot pressure control valves 71,
It is composed of a pair of switching relays 73 and 74 for switching the connection between the output terminal 72 and the output terminal of the operation lever 26A.
Note that 75 is a pump oil passage, and 76 is a tank oil passage.

Therefore, when the changeover switch 23 is in the up and down position, the changeover relay 73 operates the electric operation lever 26.
A current based on the backward tilt operation of A is supplied to the electromagnetic pilot pressure control valve 71 to switch the four-port three-position switching valve 51 to the first switching position 51b, and the switching relay 74 tilts the electric operating lever 26A forward. A current based on the operation is supplied to the electromagnetic pilot pressure control valve 72 to switch the four-port three-position switching valve 51 to the second switching position 51c. When the changeover switch 23 is in the telescopic position, the changeover relay 73 supplies a current based on the backward tilting operation of the electric operation lever 26A to the electromagnetic pilot pressure control valve 72 to change the four-port three-position changeover valve 51 to the fourth position. Switching to the 2 switching position 51c, the switching relay 74 supplies a current based on the forward tilting operation of the electric operation lever 26A to the electromagnetic pilot pressure control valve 71 to move the 4-port 3 position switching valve 51 to the first switching position 51b. Switch to.
That is, when the changeover switch 23 is in the telescopic position, the switching operation direction of the 4-port 3-position switching valve 51 is reversed. According to this configuration, the effects described in the above embodiment can be obtained by adding the electric operation lever 26A, the pair of electromagnetic pilot pressure control valves 71 and 72, and the pair of switching relays 73 and 74.
This can also be achieved by the configuration described above.

In the structure shown in FIG. 6, the embodiment (FIG. 4)
Of the pilot pressure control circuit,
The port 2 position switching valve 63 is omitted, and a 4-port 2 position switching valve 163 having the same structure is inserted between the 4-port 3 position switching valve 51 and the up / down / expansion switching valve device 25. According to this configuration, the flow direction of the pressure oil from the four-port three-position switching valve 51 does not change when the changeover switch 23 is in the up / down position, but when the changeover switch 23 is in the telescopic position, the four-port three-position does not change. Since the flow direction of the pressure oil from the switching valve 51 is switched, the same effects as described in the above embodiment can be obtained. That is, the operation lever 26
The tilting and stretching operations of the jib can be matched with the tilting direction of the jib. However, the embodiment of FIG. 4 has an advantage that the capacity of the 4-port 2-position switching valve 63 can be reduced.

Further, in addition to the structure shown in FIGS. 5 and 6, the switching operation direction of the 4-port 3-position switching valve 51 may be mechanically reversed in conjunction with the operation lever 26. That is, in the direction opposite to the tilting direction of the operation lever 26, 4
The port 3 position switching valve 51 may be mechanically configured to operate.

[0032]

According to the jib hoisting / extending / contracting device of the crane of the present invention, the cylinder speed can be set to the same level during the hoisting operation and the elongating / contracting operation, and the jib can be raised and lowered in the tilting direction of the operation lever. The compression operations can be matched.

[Brief description of the drawings]

FIG. 1 is a side view showing a crane according to an embodiment of the present invention.

FIG. 2 is a view showing a state where a telescopic boom and a jib are extended in the embodiment.

FIG. 3 is an enlarged view showing a jib portion in the embodiment.

FIG. 4 shows a jib hoisting and retracting device (P
It is a figure which shows PC valve system).

FIG. 5 is a view showing another example (EPC valve system) of the jib hoisting / contracting device.

FIG. 6 is a view showing still another example of the jib hoisting / contracting device.

FIG. 7 is a view showing a conventional jib hoisting / contracting device.

FIG. 8 is a diagram showing a case where a conventional jib hoisting / contracting device is applied to a hoisting cylinder hoisting type structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 13 Telescopic boom 16 Support shaft 17 Jib 18 Raised / lowered cylinder 19 Telescopic cylinder 20 Jib raising / lowering / expanding device 23 Switching switch 25 Raising / retractable switching valve device 26, 26A Operating lever 29 Hydraulic directional switching valve 30 Reversing means 51 4 port 3 position switching valve 51b 1st switching position 51c 2nd switching position 63 4 port 2 position switching valve (reversing means) 71, 72 Electromagnetic pilot pressure control valve 73, 74 switching relay 163 4 port 2 position switching valve (reversing means)

Claims (4)

[Claims] 1. A crane jib hoisting / contracting device for raising and lowering a telescopic jib supported at the tip of a boom via a support shaft so as to be capable of raising and lowering, wherein the jib is provided below the support shaft. An up / down cylinder that moves up and down, an extendable cylinder that extends and retracts the jib, a changeover switch, an up / down / expansion changeover valve device that is switched by the changeover switch, an operation lever that can tilt and return to a neutral position, A hydraulic direction switching valve that supplies pressure oil to one of the up-and-down cylinder and the telescopic cylinder through an expansion / contraction switching valve device and that switches between a first switching position and a second switching position in accordance with the tilting direction of the operation lever; The first switching position pressure oil side of the hydraulic direction switching valve is
The second switching position pressure oil side of the hydraulic directional switching valve is connected to the bottom side of the up / down cylinder and the telescopic cylinder via an expansion / contraction switching valve device, and is connected to the bottom of the hydraulic cylinder. A crane jib hoisting / contracting device which is connected to the head and has a reversing means for reversing a switching operation direction of the hydraulic direction switching valve in conjunction with an operation of the switching switch. 2. The crane according to claim 1, wherein
In the telescopic device, the hydraulic direction switching valve is formed by a four-port three-position switching valve that is switched and controlled by a pilot pressure, and the reversing means is configured to switch the four-port three-position switching valve based on a tilting operation of the operation lever. It is formed by a 4-port 2-position switching valve which is inserted in the middle of a pilot pressure oil passage for supplying a pilot pressure and switching the 4-port 3-position switching valve to operate in conjunction with the switching operation of the switching switch. Crane jib up / down
Telescopic device. 3. The crane according to claim 1, wherein
In the telescopic device, the hydraulic direction switching valve is formed by a four-port three-position switching valve that is switched and controlled by a pilot pressure, and the operating lever outputs an electric current having a magnitude corresponding to a tilt direction and a tilt angle. The reversing means is formed by an operating lever, wherein the reversing means includes a pair of electromagnetic pilot pressure control valves for controlling a pilot pressure supplied to the four-port three-position switching valve, and a pair of the electromagnetic pilot pressure control valves and the operating lever. The two output terminals are connected to each other, and are formed by a pair of switching relays that are switched in conjunction with the operation of the changeover switch and switch the connection between the pair of electromagnetic pilot pressure control valves and the output terminals of the operation lever. A crane jib hoisting / extension device. 4. A crane jib hoisting / contracting device for raising and lowering a telescopic jib supported at the tip of a boom via a support shaft so as to be capable of raising and lowering, wherein the jib is provided below the support shaft. An up / down cylinder that moves up and down, an extendable cylinder that extends and retracts the jib, a changeover switch, an up / down / expansion changeover valve device that is switched by the changeover switch, an operation lever that can tilt and return to a neutral position, A hydraulic direction switching valve that supplies pressure oil to one of the up-and-down cylinder and the telescopic cylinder through an expansion / contraction switching valve device and that switches between a first switching position and a second switching position in accordance with the tilting direction of the operation lever; The first switching position pressure oil side of the hydraulic direction switching valve is
The second switching position pressure oil side of the hydraulic directional switching valve is connected to the bottom side of the up / down cylinder and the telescopic cylinder via an expansion / contraction switching valve device, and is connected to the bottom of the hydraulic cylinder. A switching valve that is connected to the head side and that is provided between the hydraulic direction switching valve and the up / down / expansion / retraction switching valve device and that switches a flow direction of hydraulic oil from the hydraulic direction switching valve in conjunction with operation of the switching switch A jib hoisting and retracting device for a crane, comprising: